Electrically adjustable antennas are widely used in wireless transmissions. Apart from radiation units and reflectors, Phase Shifter Network (PSN) is a vital component of the electrically adjustable antenna. A phase shifter is mainly used in the electrically adjustable antenna to adjust a change in phase of the feed network, so as to vary the phase of each radiation unit or a group of radiation units, thereby achieving the purpose of changing a beam tilt angle in a vertical plane or a beam angle in a horizontal plane. Particularly, in the existing phase shifter network, an air strip line is usually adopted to transmit signals, and changes in phase are enabled by placing a movable medium below a specific position of the strip line.
The strip line tends to have the following defects. First, the strip line may be easily deformed due to its long and thin shape, and welding between two strip lines is sometimes required. Secondly, some parts of the PSN are fixed by screws and the metal screws may influence the passive intermodulation (PIM) performance of the PSN. Furthermore, at present the phase shifting unit(s) forming the PSN has complex structure, so it is difficult to assemble and rework. Additionally, PSN sometimes may comprise more phase shifting units. When PSN is used for environmental test, the Antenna Control Unit (ACU) cannot drive the phase shifting apparatus, which causes inconvenience in use of PSN and restricts the application of PSN.
Thus, there is a need for a phase shifting apparatus which has satisfactory PIM performance and is easy to assemble.